Such a gate is well known from the state of the art and regularly employed in sporting disciplines such as alpine skiing, cross-country skiing, canoeing or again cross-country running. It may appear as shown in FIGS. 1 and 2. FIG. 1 is a perspective view of a known type of gate. It comprises an outlet formed from two risers 1 and 2 arranged on either side of the track 3 used by the runner and placed on the departure line 4. The gate is provided with contact means which will produce an electrical signal when the runner crosses the line 4. To this effect it comprises a device 5 fixed on the riser 2. A bar 6 is hinged onto device 5. Bar 6 controls an electrical contactor (not shown) mounted in the device 5. When pushed by the runner, bar 6 pivots in the sense of arrow 7 and when it has traversed an angle of around 30.degree., operates a contact provided within the contactor. The activation of this contact starts an electronic chronograph which counts the elapsed time between the moment of opening of the bar until the moment when the runner crosses the finish line.
This simple system presents however a serious difficulty which is that of causing the starting of the chronograph to depend on the position of the runner at the moment of departure from whence there may result different times according to the position chosen. In order to explain this, reference is made to FIG. 2 which shows a top view of the gate according to the prior art and which employs the same references as those employed on FIG. 1. The bar here is shown in the closed position 6 where it is aligned along the departure line 4 and in an intermediate position 6' for which the opening angle .alpha. is of 30.degree.. For this opening angle, the contactor controlled by bar 6 is activated and the chronograph begins to count. To bring the bar from the position 6 to the position 6', one may act at 8 close to the hinge or at 9 at the opposite end. If one acts at 8, the figure shows that a very small displacement a is necessary to bring the bar from the position 6 to the position 6' while if it is at 9 that one acts, there will be required a much greater displacement b in order to obtain the same opening angle. This being the case, it is understood that the runner shown at 10 on figure 2 will have every advantage to place himself as close as possible towards the left of the figure and even in this position, to advance his right knee since in these conditions he may cross a distance b before the chronograph begins to count. Thus of two runners moving at the same speed over the same distance, one leaving at 8 and the other at 9, it is the one who will have left at 9 who will win the race.
If one designates by t the average time taken by a runner to cover a distance designated by L, by b the distance traversed before starting of the chronograph, the time gain t' will be: EQU t'=t.multidot.b/L
According to the type of course envisaged, this time gain is not negligible. In order to be convinced thereof, one may take an example drawn from a ski race of the slalom type. The competition is run over a length of about 600 meters and has an average duration for each skier of around 86 seconds. The outlet of the gate has a width of 0.75 meters between the riser 1 and 2. FIG. 2 being drawn at the scale 1/10, it is seen that if the push takes place at 9, the distance b crossed is on the order of 0.3 m (while such would be only of 0.04 m if the push had been given at a). One may thus, by applying the above formula, estimate the time gain t' at EQU t'=86.multidot.0.3/600=0.04 second.
This value may be considered as a minimum since it does not take account of the fact that the skier starts from a stopped position. Various practical measures have shown that the time gain considered may be situated between 0.04 seconds and 0.1 second. When one realizes that presently the classification of competitors depends on hundredths of a second, it will be undersood that there is a need to eliminate or at least to minimize as far as possible the advantage which one competitor may have over another based only on the manner of departure, whether this advantage be intentionally sought or not.
It is conceivable that this advantage may vary in considerable proportions. It is going to depend essentially, as has been seen, from the position taken by the runner at the departure but may also depend on other factors such as for instance width of the outlet between the risers 1 and 2.